Abstract

Clinical examination is non-invasive, but has well-recognized limitations in detecting compensated and uncompensated low flow states and their severity.

This paper describes the principles of near infra-red spectroscopy (NIRS) and the basis for its proposed use, in hypovolaemic, cardiogenic and septic shock, for assessing global and regional tissue oxygenation. The vascular occlusion test is explained. Limitations of NIRS, current controversies, and what is necessary in the future to make this technology a part of the initial and ongoing assessment of a patient, are discussed as well. The ultimate goal of such techniques is to prevent miss-assessment and inadequate resuscitation of patients, two major initiators in the development of multisystem organ failure and death.

Methods. Twenty-seven infants with bronchiolitis that needed mechanical ventilation were included in a prospective study. Regional StO2 in brain, liver, kidney and skeletal muscle tissue was measured on admission to the Intensive Care Unit (ICU), on day 1 (D1); after two to three days of mechanical ventilation (D2); on the last day of mechanical ventilation (D3) and during spontaneous breathing (D4). Measurements were conducted by in-vivo optical spectroscopy. For research purposes we divided the infants according to C-reactive protein (CRP) levels, with a cut-off value of 10 mg/ml on admission, into low (l-CRP) and high (h-CRP) groups.

Results. During mechanical and spontaneous breathing we found lower StO2 and higher FTOE for skeletal muscle at D4 compared to D1-D2 in the h-CRP group of patients. Differences between l- and h-CRP groups in rStO2 were found for brain tissue on D3, D4, and in rStO2 and FTOE for liver tissue on D3. A strong negative correlation was found between rStO2 and FTOE in all tissues. A positive correlation was found between CRP and rStO2 and negative between CRP and FTOE in skeletal muscle among all patients combined.

Conclusion. Only Infants with acute bronchiolitis in the h-CRP group have significant changes in rStO2 and FTOE in skeletal muscles during mechanical ventilation and spontaneous breathing. Regional StO2 and FTOE in all the other measured tissues never decreased below normal values.

Abstract

Background. Leukocyte counts may influence peripheral (micro) circulation due to changes in rheology. The aim of this study was to investigate a possible association between leukocyte counts and peripheral tissue oxygenation/perfusion measured with near infrared spectroscopy (NIRS) in term and preterm neonates.

Methods. In this observational study we included term and preterm neonates within the first 2 months of life, in whom peripheral tissue NIRS measurements were performed and blood samples (leukocytes and C reactive protein (CRP)) taken to investigate clinical signs of infection. Tissue-oxygenation index (TOI), fractional oxygen extraction (FTEO), oxygen delivery (DO2), oxygen consumption (VO2) and vascular resistance (VR) were measured by NIRS and venous occlusion method. TOI, FTOE, DO2, VO2 and VR were correlated to leukocyte counts on the same day and maximal CRP levels within 24 hours (CRP max).